This fan battle has been going on for a really long time and has had fans going at it for years. Dragon Ball fans clearly say it would be Goku because he can rip apart planets with only powering up, but comic fans believe it's Superman.
I am a great fan of both and I don't want to be biased, so I'll do my best not to be. However, to me, the answer to this question was obvious all along. Who would win? Both. Depending on the situation, of course, and this small story will be delving into that. Okay, so what do we know about them?
Both are aliens from dead civilizations, the last of their kind who found another home in another planet and it's people. Both have incredible powers and are fighting for good. Still, their levels of power is different and this difference decides who will come out triumphant.
It all depends on what the situation is or how much they prep for battle. But let's just say that Superman and Goku meet in a field, without any civilians around. They start fighting. Why? It doesn't matter now. Many believe that this debate would be useless because the battle would never happen. They are good guys and would not fight. Well, this isn't true since we all know Goku, he loves to fight with everyone, especially strong opponents. He would beg Superman for a battle, even if it would not be serious or to the death. But let's just say that they do so as an all out training.
Goku uses Ki energy which is the balanced force in his body which is created by his physical, emotional and mental existence. He can manipulate this energy to be used as a body enhancer to be stronger, faster and use his abilities. We can say that this is like sunlight for Superman. Without Ki, he is only barely stronger than an average human. As a Saiyan, he heals faster than a human, gets stronger after each battle, lost or won. However, Ki is not magic, the DBZ Universe has clearly stated that. As such, it can't be used as a weakness for Superman.
Kal-El is fueled by the sun which gives him his powers. Without them, he is approximately three times stronger and faster than a normal human because of his home planet's increased gravity strength.
Okay, so what about the questions the fandom used to ask? Let's list some.
Superman can't fight in superspeed, he can only travel. Is this true? I don't know, I have seen it in comics before, so I don't know what Superman's speed capabilities are but for the sake of the argument, let's say he can't. So, Goku can do battle faster. It all does not matter if he can't harm Superman since he's invulnerable.
Strength. Superman clearly wins. Why? See the picture.
Superman has been bench-pressing the weight of the entire planet for FIVE DAYS. I have seen the whole DBZ series and read the mangas. I have never seen Goku being even close to this feat. We have seen him banged up and beaten many times and Goku has been hurt by normal things like slaps, swords and such.
One full power punch from Superman would obliterate Goku. But he can't hit him if he can't catch him, which we've seen with Trunk's battle against Cell. It all comes down to durability and stamina.
That's right! Think about it. Everything we could come up with stops when we face the facts. Goku is faster than Superman and he can use Ki in devastating ways like the Kamehameha wave. Superman is much stronger than Goku and much more durable. Who would win? The one who's left standing. Goku isn't invulnerable like Superman but he can get in more attacks and can do more damage. Goku however is weaker and can't take as much damage but is harder to catch. Seems like a circle going forever, does it?
So, the man who would win is... Superman! Why? Superman's sunlight given powers are longer lasting than Goku's Ki energy. We have seen saiyans tire out and empty their energy reserves in battle. Superman has been bench-pressing the Earth's weight for five days in the center of the planet where there is no sunlight which means that he has been efficiently doing peak capacity training for five days without tiring out. The only chance Goku has is if he can do one of his most powerful attacks, like the Super Dragon Fist or the minimum of an omega level Spirit Bomb without tiring out.
So that's it, that's my opinion. I'm ready for the flames :D